Water-based fluids such as, for example, drilling fluids, milling fluids, mining fluids, water-based metal working fluids, food additives and water-based paints, are useful in a variety of industrial applications. It is well known to those skilled in the art of drilling wells to tap subterranean deposits of natural resources, such as gas, geothermal steam or oil, especially when drilling by the rotary method or the percussion method wherein cuttings must be removed from the bore hole, it is necessary to use a drilling fluid.
The use of water-based fluids in, for example, workover and completion fluids in oil field operations is also well known to those skilled in the art. Workover fluids are those fluids used during remedial work in a drilled well. Such remedial work includes removing tubing, replacing a pump, cleaning out sand or other deposits, logging, etc. Workover also broadly includes steps used in preparing an existing well for secondary or tertiary recovery such as polymer addition, micellar flooding, steam injection, etc.
Completion fluids are those fluids used during drilling and during the steps of completion, or recompletion, of the well. Completion operation can include perforating the casing, setting the tubing and pump, etc. Both workover and completion fluids are used in part to control well pressure, to stop the well from blowing out while it is being completed or worked over, or to prevent the collapse of casing from over pressure.
Chemicals are added to the water-based fluids for various reasons that include, but are not limited to, controlling water loss, increasing viscosity, reducing corrosion, inhibiting biodegradation, and increasing the density of the fluids. For example, chemicals such as, for example, water-thickening polymers serve to increase the viscosity of the water-based fluids, when used as workover fluids or completion fluids, to retard the migration of the brines into the formation and to lift drilled solids from the wellbore.
However, the above-discussed chemicals are often unstable at the temperatures of various oil reservoirs and are often subject to biodegradation. Furthermore, fluids containing the chemicals often lose their viscosity or water loss control, or both, after aging at low temperatures.
It is therefore highly desirable to develop a composition and a process for applications that require high viscosity development. It is also highly desirable to develop a composition and a process which retain proper viscosity or control water loss, or both, of the composition over a broad range of conditions. It would also be a significant contribution to the art if a composition and process that are capable of controlling water loss under a variety of conditions in oil field work.